油基钻井液用改性碳纳米管纳微米封堵剂

Modified Carbon Nanotube as Nano-micro Plugging Agent in Oil-based Drilling Fluid

倪晓骁 史赫 闫丽丽 王建华 程荣超 张家旗 刘雨艳

NI Xiaoxiao SHI He YAN Lili WANG Jianhua CHENG Rongchao ZHANG Jiaqi LIU Yuyan

为改善页岩油气水平井钻进过程中因钻井液封堵性能差而引起的井壁失稳问题，首先，对川南龙马溪组页 岩组成和井壁失稳的原因进行了分析；然后，以十六烷基三乙氧基硅烷、氨丙基三乙氧基硅烷和活性碳纳米管为 原料，合成了油基钻井液用纳微米封堵剂（NP-1），分别利用红外光谱分析、热重分析、透射电镜和表面润湿性测 试分析其结构和物理化学特性，考察了其与油基钻井液的配伍性；最后，通过岩心突破压力、压力传递、三轴抗压 强度等测试评价其封堵性能，分析了纳微米封堵剂的作用机理，并进行了现场应用。结果表明，川南龙马溪组页 岩纳微米孔喉较发育，毛细自吸现象严重，使得液相不断侵入井壁，最终导致井壁失稳。NP-1 的直径为30～50 nm，长度处于微米级别，表面疏水亲油，在385.2 ℃以下的热稳定性良好。NP-1 与油基钻井液具有良好的配伍 性和稳定性。在常规油基钻井液中加入3% NP-1，在180 ℃下老化热滚16 h 后的高温高压滤失量由2.8 mL降至 1.8 mL。含有NP-1 的油基钻井液能有效封堵岩心端面，从而提高岩心突破压力，阻止岩心压力传递，稳定岩心内 部结构和抗压强度，实现维持井壁稳定的目的。现场应用结果表明，NP-1 能有效改善邻井因钻井液封堵能力弱 而引起的井漏、井壁失稳等技术难题，处理后的平均井径扩大率仅为5.61%。该纳微米封堵剂在油基钻井液中对 页岩具有优异的封堵效果，为川南类似复杂页岩气井的高效钻探提供了借鉴。

In order to improve the wellbore instability caused by poor plugging performance of drilling fluid during the drilling of shale oil and gas horizontal wells，firstly，the composition and the wellbore instability of Longmaxi shale in South Sichuan were analyzed. Then n-cetyl-triethoxy-silane，aminopropyl-triethoxy-silane and activated carbon nanotube were used as raw materials to synthesize the nano-micron plugging agent（NP-1）for oil-based drilling fluid. Its structural and physicochemical properties were analyzed by Fourier transform infrared，thermogravimetric，transmission electron microscope and surface wettability，and then its compatibility with oil-based drilling fluid was investigated. Finally，the plugging performance was evaluated by breakthrough pressure，pressure transmission and triaxial compressive strength. The mechanism was analyzed and then the field application was carried out. The results showed that there were lots of developed pore throats in size of nanometer and micron-meter and serious capillary spontaneous imbibition of shale in South Sichuan. As a result，the liquid would permeate into the wellbore continuously， which would lead to wellbore instability. The diameter of NP-1 was in the range of 30—50 nm，the length was in the micron-meter， the surface wettability was hydrophobic and lipophilic，and then the thermal stability was good below 385.2 ℃. NP-1 had good compatibility and stability with oil-based drilling fluid. The high temperature and high pressure filtration loss after aging 16 h at 180 ℃ was reduced from 2.8 mL to 1.8 mL after adding 3% NP-1 to ordinary oil-based drilling fluid. The oil-based drilling fluid with NP-1 could effectively plug the end face of shale，which could improve the breaking pressure，prevent the pressure transmission，stabilize the core internal structure and compressive strength，and then maintain the wellbore stability. Field application results showed that NP-1 could effectively alleviate the lost circulation and wellbore instability of adjoining well caused by the weak plugging ability of drilling fluid. The enlargement rate of well diameter in average was only 5.61% after treating. NP-1 had excellent plugging performance for shale in oil-based drilling fluid. It provided a reference for efficient drilling of similar complex shale gas wells in South Sichuan.

10.19346/j.cnki.1000-4092.2023.04.002